Leveling instrument.



H. WILD.

LEVELING INSTRUMENT. APPLICATION FILED Aue.2. 1910.

Patented Nov. 16, 1915.

WM L HEINRICH WILD, 01mm, GERMANY, ASSIGNOR TO THE FIRM or CARL znrss,or

1 A JENA, GERMANY. I

' LEVELI'NG INSTRUMENT.

Specification of Letters Patent.

Patented Nov. 16, 1915.

To all whom it may concerm' Be it known that I, HEINRICH WILD, a citizenof the German Empire, residing at Carl-Zeiss strasse, Jena, in the GrandDuchy of Saxe-Weimar, Germany, have invented a new and useful LevelingInstrument, of which the following is a specification.

The invention relates to leveling instru-' be unscrewed from thetelescope and screwed on again after changing it end for end or that itcan be turned by 180 about a vertical axis. In both cases theapproximate adjustment of the instrument is'lost, the restoring of whichentails a great loss of time.

According to the present invention the spirit level can be used in theopposite direction, without giving it .a different position relative tothe telescope, if the sighting telescope itself is so constructed thatit can be used in the opposite direction. Such an arrangement was usedby Le Cyre with the sighting telescopes of a'range finder and isdescribed on page 250 and shown on Plate XVI of Des instruments pour lamesure des distances by J. de Marre, (Paris 1880). Le Cyre fitted at theends of a tube two mark plates and within it two equal objectives, eachat a very small distance from a mark plate and of such focal length,that its prin-.

cipal focal plane passes through the mark which is adjacent to the otherobjective. Two lines of sight of approximately opposite direction thenresult, each determmed by the optical center of an objective and themark in its principal focal plane. An

equivalent arrangement is obtamed, when both objectives are given thesame focal length and the marks are fixed directly on the objectives. Amixed form of the two arrangements can also be employed. An eye piecewas hinged to either end of the tube by Le Cyre. Instead of this asingle eye plece, adapted to be placed on either end of the tube, canalso be used.

In order to render a sighting telescope of this description capable ofbeing focused for use as a leveling telescope, it is sulficlent to makeone objective shiftable. But the same result will be obtained,ifsimilarly as 1n the common leveling telescope a special focusing lensis provided between objective and mark platea negative orpositive,-shiftable lens be provided between the two objectives.

In the annexed drawing: Figure 1 is a diagrammatic representation of aninstrument according to the invention, showing its manipulation. Fig. 2is an elevation, partly in section, of a leveling telescope accordlng tothe invention.

In Fig. 1 the spirit level a is re resented with its scales 6 b and c 0first with the bubble in the zero position before reversing) by fulllines, and a. second time (after reversing with the bubble again broughtinto the zero position) by dotted lines. The two corresponding positionsof the sightin tele scope are indicated by I and II, whic may be takento represent the values read on the staff. In both the objective (1projects the image of the staff in the field of the mark e of. theobjective e. The lenses f and 9 represent the eye piece. The mean I+IIof the two readings is, as is well-known, independent of the position ofthe spirit level relative to the line of sight and is too small or toogreat by only the half of the spirit level error, if by spirit levelerror is understood the error in the reading, which corresponds to therelative inclination of the two axes, which pertain, before and afterreversing, to the spirit level with its bubble brought into the zeroposition. According as this angle may be-open or closed toward the eyepiece, the spirit level error has a positive or a negative sign and themean of the two readings I and II is too great or too small. Iftherefore by changing the spirit level end for end the spirit levelerror is caused to change its sign and of these two hasthe same butopposite error to the first mean I H a The correct reading is gainedfrom the mean of the two means In the case of the arrangement accordingto the invention the second pair of readings is arrived at, by fittingthe eye piece f g to the other end of the telescope and rotating thetelescope in the azimuth by 180, so that now the objective 6 projectsthe image of the stafi in the field of the mark d.

In Fig. l the position of the new sighting telescope before and afterreversing is also represented, while the third and fourth positions ofthe spirit level a do not visibly differ from the first and secondpositions on account of the symmetrical form of the spirit level, and onaccount of the position assumed for the axis of azimuthal rotation inthe plane of symmetry of the spirit level.

The adjustment on the basis of the correct reading can be carried out invarious ways. The simplest is to give to the readinglthe value of thecorrect reading by manipulating the tilting screw of the telescope andthen to bring the level bubble into zero position by shifting the scale6 I). But then only reading 1 may be worked with. Should it be requisitefor specially accurate measurements to make use of the reversion, i. e.to

always take readings I and IT, in order to value I II 2 must, byshifting the scale 6 b or the scale c c or both, be made equal to thecorrect reading. The spirit level error has then become zero: the spiritlevel axes lie parallel to each other.

In Fig. 2 the spirit level a is fitted instead of with two scales withtwo pairs of marks 5 72 and 0 0, which are rigidly joinedtogether andmay be adjusted by the screws a which secure them to the spirit levelcasing, being slackened, the piece carrying the pairs of marks shiftedin the direction of the spirit level axis and the screws tightenedagain. The eye piece g can he slid onto either end of the telescope, asthe case may be. The two objectives d and e are at the same time thecarriers of the marks (1 and 0 LA dispersive lens h, which is madeshiftable in the usual way, serves for the focusing.

The instrument is journaled in a support 71 and can be set in thevertical plane, being hinged to a base it and further connected withthis base by a tilting screw Z.

I claim:

In a leveling instrument the combination with a sighting telescope, of aspirit level fixed to the telescope, and a support, in which thetelescope is journaled, so as to be rotatable on its axis through 180,the telescope having an objective at either end, a mark at either end inthe focus of the objective placed at the other end, and optical meansfor observing either mark together with the image projected by theobjective placed at the other end.

HEINRICH D.

Witnesses PAUL Km'iona, Amman MAcKnDANz.

